Usually, a fuel cell has an optimal range for the operation temperature (for example, the maximum power generation efficiency can be obtained at the temperature) according to characteristic of the fuel cell. In order to control the operation temperature of the fuel cell within the optimal range, the temperature of the cooling fluid of the fuel cell is required to be controlled within a predetermined range.
From this, for example, in a fuel cell system of Patent document 1, when a heating operation is performed in the vehicle, a fuel cell cooling circuit is connected to an air-conditioning circuit. When the cooling water of the fuel cell cooling circuit is used for the heating operation, the heat generating amount and the heat emitting amount are controlled to be balanced in the fuel cell system. For example, when the heat generating amount is small, an electric heater is activated to complement the insufficiency in the heat generating amount, such that the temperature of the cooling water of the fuel cell cooling circuit is restricted from having large variation (large decreasing). Furthermore, the temperature of the cooling water is detected at the outlet side of the fuel cell. Based on this outlet temperature, the heat generating amount in the fuel cell system is controlled, or the fuel cell cooling circuit is connected to or disconnected from the air-conditioning circuit, such that the temperature of the cooling water of the fuel cell cooling circuit is controlled within the predetermined range.
Moreover, Patent document 2 is known as a conventional air-conditioner for a vehicle. The air-conditioner of Patent document 2 is applied to a vehicle which has a fuel cell as a drive source, and includes a heater core which heats air for air-conditioning by using the cooling water of the fuel cell as a heat source, and a first indoor unit and a second indoor unit which heat the air for air-conditioning by using high-temperature refrigerant of a heat pump equipment as a heat source. The heater core, the first indoor unit, and the second indoor unit are arranged in an air-conditioning case, in order of the second indoor unit, the heater core, and the first indoor unit from the upstream side to the downstream side in the flow of the air for air-conditioning.
When the temperature of the cooling water of the fuel cell is higher than a reference temperature, and when the passenger compartment is heated (at a heating operation mode), the air for air-conditioning is heated as follows. That is, when the temperature of the cooling water exceeds the target blow-off temperature of air blown-off into the passenger compartment by +5° C. or more, the heat pump equipment is suspended, and the air for air-conditioning is heated only with the heater core.
On the other hand, when the temperature of the cooling water is less than the value calculated by adding +5° C. to the target blow-off temperature of air, the heat pump equipment is operated, and the air for air-conditioning is heated using the first indoor unit, the second indoor unit, and the heater core. In this case, the air for air-conditioning heated by the heater core can be further heated with the first indoor unit. Even when the temperature of the cooling water is low, the cooling water can be used as a heat source for heating.
Moreover, the temperature of the cooling water of the fuel cell is lower than the reference temperature, the fuel cell is operated to be warmed (at a warm-up operation mode). At this time, high-temperature refrigerant is made to flow in the second indoor unit, thereby heating the heater core, i.e., the cooling water of the fuel cell, at the downstream side.
However, in the fuel cell system of Patent document 1, when the heat generating mount is shorted in the fuel cell system, the shortage is complemented by the electric heater, so the efficiency is low. Further, the drive mileage of the vehicle is reduced since the electric power of the fuel cell is used.
Moreover, in the air-conditioner of Patent document 2, the two indoor units are needed, so it is difficult to arrange the two indoor units in the air-conditioning case.
Moreover, the air-conditioner of Patent document 2 does not have a concept that the temperature of the cooling water of the fuel cell is controlled within the predetermined range. Heat is emitted from the heater core while the combination of the heater core, the first indoor unit and the second indoor unit is determined so as to meet the target blow-off temperature for the passenger compartment. Therefore, when the heat core performs excessive heat emitting, the temperature of the cooling water cannot be kept constant.
Moreover, at the warm-up operation mode of the air-conditioner of Patent document 2, the second indoor unit can heat the cooling water of the heater core. However, the temperature of the air for air-conditioning is lowered when passing the heater core after heated by the second indoor unit. Thus, the low-temperature air will be blown off into the passenger compartment, and an occupant of the vehicle feels uncomfortable.